Antagonism to muscarinic receptors are known to cause bronchodilation, gastrointestinal hypanakinesis, gastric hyposecretion, dry mouth, mydriasis, suppression of bladder contraction, hypohidrosis, tachycardia and the like [cf. Basic and Clinical Pharmacology, 4th ed., APPLETON & LANGE, pp. 83-92 (1989) and Drug News & Perspective, 5(6), pp. 345-352 (1992)].
It has recently been made clear that there are at least three subtypes of muscarinic receptors; M1 receptors being present mainly in the brain; M2 receptors, mainly in the heart, and M3 receptors, on smooth muscles and glandular tissues. Whereas, all of the large number-of compounds heretofore known to exhibit antagonism to muscarinic receptors non-selectively antagonize the three subtypes of muscarinic receptors. Consequently, attempts to use these compounds as therapeutic or prophylactic agents for diseases of the respiratory system have caused undesirable side effects such as dry mouth, nausea and mydriasis. Still in addition, particularly serious side effects associated with the central nervous system, such as dementia, attributable to M1 receptors and those associated with the heart, such as tachycardia mediated by M2 receptors pose problems and their solution has been strongly in demand.